1. Field of the Invention
This invention relates to a semiconductive ceramic composition for a semiconductive ceramic capacitor, and more particularly to a semiconductive ceramic composition suitable for use for manufacture of a boundary insulation type semiconductive ceramic capacitor.
2. Description of the Prior Art
A semiconductive ceramic capacitor serving as a passive electronic circuit element is generally classified into two types, i.e. a boundary-layer type and a surface-layer type. The boundary-layer type semiconductive ceramic capacitor includes a boundary insulation type one and the surface-layer type semiconductive ceramic capacitor includes a barrier-layer type one and a reduction reoxidation type one.
However, it was found that the conventional semiconductive capacitors have the following disadvantages.
The boundary insulation type semiconductive capacitor is relatively decreased in capacity and dielectric strength. The barrier-layer type one is deteriorated in frequency characteristics, increased in dielectric loss (tan .delta.) and decreased in dielectric strength. The reduction reoxidation type one is deteriorated in frequency characteristics and increased in temperature characteristics and dielectric loss. Such disadvantages are caused due to the fact that a semiconductive ceramic composition which is capable of providing a semiconductive ceramic capacitor free of the above-noted disadvantages is not still developed.